1966 Plymouth Valiant /6 & Holley 1945 carb can only get to idle at 1250rpm. How to get a lower idle without dying?

yeah, it's in pieces. Probably contributes to the rubbing against the steering linkage.
It's possible, I suppose, but it'll have nothing to do with it rubbing on the k frame. If you can weld, I'd just modify the front of the pan. Be a lot easier than finding an early a body pan.